First, you must ensure pin 28 of the LM8650 is NOT connected to anything else! Or you might destroy your clock radio when connecting pin 28 to Vss.
In some cases, you may find there is a spot already for a jumper wire to Vss that’s just not been put in at the factory.

After adding the wire, you’ll see that time now goes in 24 hour style…for the “2” in the tens position of hours, it will just light the top segment of what would be a numeral one instead of displaying a “2”, for those displays with only a “1” in the tens hour place.